Systems and methods for overcoming stiction

ABSTRACT

An electromechanical system includes a structural plate in contact with a stop and an actuator activated by a force for creating a movement of the stop relative to the structural plate, wherein the movement is sufficient to overcome stiction forces between the structural plate and the stop.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of, and claims the benefit of,co-pending, commonly assigned U.S. patent application Ser. No.10/719,177 entitled “SYSTEM AND METHODS FOR OVERCOMING STICTION” byDavid Miller, et al. (Attorney Docket No. 019930-002840US), filed Nov.20, 2003, which application is a divisional of U.S. patent applicationSer. No. 10/087,040 (now U.S. Pat. No. 6,856,068, issued on Feb. 15,2005) entitled “SYSTEM AND METHODS FOR OVERCOMING STICTION” by DavidMiller, et al. (Attorney Docket No. 019930-002800US), filed Feb. 28,2002, the entire disclosure of each of which are herein incorporated byreference for all purposes.

BACKGROUND OF THE INVENTION

This invention relates generally to the field ofmicro-electrical-mechanical systems (MEMS), and in particular, toimproved MEMS devices and methods for their use with fiber-opticcommunications systems.

The Internet and data communications are causing an explosion in theglobal demand for bandwidth. Fiber optic telecommunications systems arecurrently deploying a relatively new technology called dense wavelengthdivision multiplexing (DWDM) to expand the capacity of new and existingoptical fiber systems to help satisfy this demand. In DWDM, multiplewavelengths of light simultaneously transport information through asingle optical fiber. Each wavelength operates as an individual channelcarrying a stream of data. The carrying capacity of a fiber ismultiplied by the number of DWDM channels used. Today DWDM systemsemploying up to 80 channels are available from multiple manufacturers,with more promised in the future.

In all telecommunication networks, there is the need to connectindividual channels (or circuits) to individual destination points, suchas an end customer or to another network. Systems that perform thesefunctions are called cross-connects. Additionally, there is the need toadd or drop particular channels at an intermediate point. Systems thatperform these functions are called add-drop multiplexers (ADMs). All ofthese networking functions are currently performed byelectronics—typically an electronic SONET/SDH system. However SONET/SDHsystems are designed to process only a single optical channel.Multi-wavelength systems would require multiple SONET/SDH systemsoperating in parallel to process the many optical channels. This makesit difficult and expensive to scale DWDM networks using SONET/SDHtechnology.

The alternative is an all-optical network. Optical networks designed tooperate at the wavelength level are commonly called “wavelength routingnetworks” or “optical transport networks” (OTN). In a wavelength routingnetwork, the individual wavelengths in a DWDM fiber must be manageable.New types of photonic network elements operating at the wavelength levelare required to perform the cross-connect, ADM and other networkswitching functions. Two of the primary functions are optical add-dropmultiplexers (OADM) and wavelength-selective cross-connects (WSXC).

In order to perform wavelength routing functions optically today, thelight stream must first be de-multiplexed or filtered into its manyindividual wavelengths, each on an individual optical fiber. Then eachindividual wavelength must be directed toward its target fiber using alarge array of optical switches commonly called an optical cross-connect(OXC). Finally, all of the wavelengths must be re-multiplexed beforecontinuing on through the destination fiber. This compound process iscomplex, very expensive, decreases system reliability and complicatessystem management. The OXC in particular is a technical challenge. Atypical 40-80 channel DWDM system will require thousands of switches tofully cross-connect all the wavelengths. Conventional opto-mechanicalswitches providing acceptable optical specifications are too big,expensive and unreliable for widespread deployment.

In recent years, micro-electrical-mechanical systems (MEMS) have beenconsidered for performing functions associated with the OXC. Such MEMSdevices are desirable because they may be constructed with considerableversatility despite their very small size. In a variety of applications,MEMS component structures may be fabricated to move in such a fashionthat there is a risk of stiction between that component structure andsome other aspect of the system. One such example of a MEMS componentstructure is a micromirror, which is generally configured to reflectlight from two positions. Such micromirrors find numerous applications,including as parts of optical switches, display devices, and signalmodulators, among others.

In many applications, such as may be used in fiber-optics applications,such MEMS-based devices may include hundreds or even thousands ofmicromirrors arranged as an array. Within such an array, each of themicromirrors should be accurately aligned with both a target and asource. Such alignment is generally complex and typically involvesfixing the location of the MEMS device relative to a number of sourcesand targets. If any of the micromirrors is not positioned correctly inthe alignment process and/or the MEMS device is moved from the alignedposition, the MEMS device will not function properly.

In part to reduce the complexity of alignment, some MEMS devices providefor individual movement of each of the micromirrors. An example isprovided in FIGS. 1A-1C illustrating a particular MEMS micromirrorstructure that may take one of three positions. Each micromirror 116 ismounted on a base 112 that is connected by a pivot 108 to an underlyingbase layer 104. Movement of an individual micromirror 116 is controlledby energizing actuators 124 a and/or 124 b disposed underneath base 112on opposite sides of pivot 108. Hard stops 120 a and 120 b are providedto limit movement of base 112. Energizing left actuator 124 a causesmicromirror 116 to tilt on pivot 108 towards the left side until oneedge of base 112 contacts left hard stop 120 a, as shown in FIG. 1A. Insuch a titled position, a restorative force 150, illustrated as adirection arrow, is created in opposition to forces created when leftactuator 124 a is energized.

Alternatively, right actuator 124 b may be energized to cause themicromirror 116 to tilt in the opposite direction, as shown in FIG. 1B.In such a titled position, a restorative force 160, illustrated as adirection arrow, is created in opposition to forces created when rightactuator 124 b is energized. When both actuators 124 are de-energized,as shown in FIG. 1C, restorative forces 150, 160 cause micromirror 116to assume a horizontal static position. Thus, micromirror 116 may bemoved to any of three positions. This ability to move micromirror 116provides a degree of flexibility useful in aligning the MEMS device,however, alignment complexity remains significant.

In certain applications, once the micromirror is moved to the properposition, it may remain in that position for ten years or more. Thus,for example, one side of an individual micromirror may remain in contactwith the hard stop for extended periods. Maintaining such contactincreases the incidence of dormancy related stiction. Such stictionresults in the micromirror remaining in a tilted position after theactuators are de-energized. Some theorize that stiction is a result ofmolecule and/or charge build-up at the junction between the micromirrorand the hard stop. For example, it has been demonstrated that anaccumulation of H₂O molecules at the junction increases the incidence ofstiction.

In “Ultrasonic Actuation for MEMS Dormancy-Related Stiction Reduction”,Proceedings of SPIE Vol. 4180 (2000), Ville Kaajakari et al. describe asystem for overcoming both molecule and charge related stiction. Thesystem operates by periodically vibrating an entire MEMS device toovercome stiction forces. While there is evidence that vibrating theentire MEMS device can overcome stiction, such vibration causestemporary or even permanent misalignment of the device. Thus, freeing anindividual micromirror often requires performance of a costly alignmentprocedure. Even where the device is not permanently misaligned by thevibration, it is temporarily dysfunctional while the vibration isoccurring.

Thus, there exists a need in the art for systems and methods forincreasing alignment flexibility of MEMS devices and for overcomingstiction in MEMS devices without causing misalignment.

SUMMARY OF THE INVENTION

The present invention provides improved MEMS devices for use with alloptical networks, and methods of using and making the same. Therefore,some embodiments of the invention include a structural plate comprisinga micromirror. For example, the present invention may be used with theexemplary wavelength routers described in co-pending U.S. patentapplication Ser. No. 09/422,061, filed Nov. 16, 1999, the completedisclosure of which is herein incorporated by reference.

Embodiments of the present invention comprise methods and apparatusrelated to overcoming stiction in electro-mechanical devices. Forexample, some embodiments provide methods for overcoming stictionelectromechanical systems. The methods can include providing a baselayer with a contact area or with a stop disposed on the base layer. Astructural plate is disposed above the base layer with one side of thestructural plate in contact with the contact area or stop. At the pointwhere the structural plate contacts the contact area, a stiction forceimpedes movement of the structural plate away from the contact area. Toovercome this stiction force, a local vibration is created at or nearthe contact area.

In some embodiments, the local vibration is caused by mechanical contactat or near the contact area. In other embodiments, the local vibrationis caused by exciting a mass near the contact area at a frequency at ornear the resonant frequency of the mass. In yet other embodiments, thelocal vibration is caused by activating and de-activating an actuatorsuch that a serpentine structure or other spring structure isrepetitively moved resulting in a vibration.

Yet other embodiments of the present invention provide systems capableof overcoming stiction forces. Such systems can include a base layerwith a structural plate supported above the base layer by a pivot. Thestructural plate is moveable along a movement path until it contacts astop located at a position along the movement path. Stiction forces canresult at the contact between the structural plate and the stop. Toovercome the stiction forces, a local vibration element is provided ator near the contact between the stop and the structural plate. Thevibration element provides local vibration sufficient to overcome thestiction forces.

The summary provides only a general outline of the embodiments accordingto the present invention. Many other objects, features and advantages ofthe present invention will become more fully apparent from the followingdetailed description, the appended claims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the Figs. which are describedin remaining portions of the specification. In the figures, likereference numerals are used throughout several to refer to similarcomponents. In some instances, a sub-label consisting of a lower caseletter is associated with a reference numeral to denote one of multiplesimilar components. When reference is made to a reference numeralwithout specification to an existing sub-label, it is intended to referto all such multiple similar components.

FIGS. 1A, 1B, and 1C are cross-sectional diagrams of a tiltingmicromirror controlled by actuation of different actuators;

FIG. 2A is a cross-sectional diagram of a tilting structural platesurrounded on either side by actuators including overlying vibrationalstructures according to embodiments of the present invention;

FIGS. 2B and 2C are cross-sectional diagrams illustrating movement theoverlying vibrational structures of FIG. 2A according to embodiments ofthe present invention;

FIGS. 3A and 3B are cross-sectional diagrams illustrating embodiments ofthe actuators of FIG. 2 according to the present invention;

FIG. 4 is a cross-sectional diagram of a tilting structural platesurrounded on either side by vibrating stops according to embodiments ofthe present invention;

FIG. 5A is a cross-sectional diagram illustrating an embodiment of thestops of FIG. 4 which are capable of vibrating both horizontally andvertically and either passively or actively according to embodiments ofthe present invention;

FIGS. 5B and 5C are cross-sectional diagrams illustrating an embodimentof the stops of FIG. 4 which are capable of vibrating verticallyaccording to embodiments of the present invention

FIGS. 6A and 6B are cross-sectional diagrams illustrating embodiments ofthe actuators of FIG. 4 which are capable of vibrating horizontallyaccording to embodiments of the present invention;

FIG. 7 illustrates an amplitude curve for a mass excited at or near itsnatural frequency;

FIG. 8A is a cross-sectional diagram of a tilting structural plateincluding vibrational elements integral thereto according to embodimentsof the present invention;

FIG. 8B is a top level diagram of the tilting structural plate of FIG.8A;

FIG. 8C illustrates the tilting structural plate of FIG. 8A in a lefttilt position with the vibrational element flexed according toembodiments of the present invention;

FIGS. 8D and 8E illustrate an embodiment of the present inventionincluding connected vibrational and movement actuators;

FIG. 9 is a cross-sectional diagram of a tilting structural plate systemincluding a vibrational beam according to embodiments of the presentinvention;

FIG. 10 is a top level diagram of a plurality of vibrational actuatorsinterconnected according to embodiments of the present invention;

FIGS. 11A, 11B, and 11C are schematic top, side, and end views,respectively, of one embodiment of a wavelength router that usesspherical focusing elements;

FIGS. 12A and 12B are schematic top and side views, respectively, of asecond embodiment of a wavelength router that uses spherical focusingelements; and

FIG. 13 is a schematic top view of a third embodiment of a wavelengthrouter that uses spherical focusing elements; and

FIGS. 14A and 14B are side and top views of an implementation of amicromirror retroreflector array.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

1. Definitions

For purposes of this document, a structural plate refers to asubstantially planar structure disposed on a pivot. The structural platecan be a rectangular plate, or other such member, capable of movement onthe pivot. Such flexure movement from a static position is opposed by arestoring force developed near the contact between the pivot and thestructural plate. Thus, the structural plate can be deflected byapplying a force to the beam and when the force is removed, thestructural plate returns to a static position. Such structural platescan include a cantilever beam where one edge of the structural plate iscloser to the pivot than an opposite edge.

The pivot can be any member capable of supporting the structural platein a way that allows the structural plate to deflect or tilt to one ormore sides. For example, the pivot can be a post disposed near thecenter of a rectangular shaped structural plate. Alternatively, thepivot can be a rectangular shaped plate disposed across a pivot axis ofthe structural plate. Yet another alternative includes a series of twoor more posts disposed across a pivot axis of the structural plate.Pivots can also be a complex structure allowing for the movement of asupported structural plate. For example, a pivot can be a bending ortorsion element, or a hinged element. Thus, one of ordinary skill in theart will recognize a number of other members and/or geometries which aresuitable as pivots.

2. Introduction

Embodiments of the invention are directed to MEMS methods and deviceswhich use localized vibration to overcome stiction forces. Such methodsof localized vibration can include creating a mechanical vibration at ornear locations prone to stiction forces. Such areas prone to stictionforces can include, for example, areas where a tilted structural platecontacts a base layer or a hard stop formed above a base layer. In someembodiments vibration is localized to a particular structural plate,while in other embodiments, vibration is localized to a group ofstructural plates. The localized vibration can include vibration along avertical vector, a horizontal vector, or a combination of vertical andhorizontal vectors.

In various embodiments, vibrational structures are formed at or nearlocations prone to stiction forces. Such vibrational structures can beactuated to create localized vibration, which is useful for overcomingstiction forces. The vibrational structures can include a mass which isexcited by an external force, such that the mass vibrates. Othervibrational structures can include elements formed to utilize theelastic properties of the elements to generate vibrations local to theelement. Such vibrational structures can be coupled to or integral witheither a base layer, a structural plate, or a combination thereof.Structures according to the present invention can be fabricatedaccording to MEMS fabrication techniques known in the art, or any otherapplicable techniques known in the art.

In other embodiments, localized vibration can be created by tapping amechanical element at or near the area prone to stiction forces. Suchtapping can be done at a variety of frequencies. Thus, the presentinvention provides a number of systems and methods for overcomingstiction through use of localized vibration. As will be apparent toanyone of ordinary skill in the art, the systems and methods of thepresent invention are applicable to a wide variety of applications wherestiction forces are involved.

3. Vibration Through Excitation by a Direct Current (DC) Potential

FIG. 2A illustrates an embodiment of the present invention applied to astructural plate micromirror system 200. Specifically, FIG. 2Aillustrates structural plate micromirror system 200 with a structuralplate 220 in a static horizontal position. Structural plate 220 issupported above a base layer 210 by a pivot 224 and a micromirror 222 isdisposed on structural plate 220. Structural plate 220, includingmicromirror 222, can be deflected to either the right or the left abouta pivot point 226, which in some embodiments is located at the junctionof structural plate 220 and pivot 224. Pivot 224, similar to otherpivots discussed herein, can be a complex structure allowing for themovement of a supported structural plate. For example, pivot 224 can bea bending or torsion element, or a hinged element.

A left actuator 230 is used to deflect structural plate 220 to the leftand a right actuator 232 is used to deflect structural plate 220 to theright. Structural plate 220 can be deflected to the left such that itcontacts a left stop 260. Left stop 260 includes a left vibrationalactuator 250 and a left overlying structure 240. Similarly, structuralplate 220 can be deflected to the right such that it contacts a rightstop 262 which includes a right vibrational actuator 252 and a rightoverlying structure 242.

In operation, left actuator 230 is actuated, along with rightvibrational actuator 252, by application of a DC voltage, VR. Thepotential difference between VR and structural plate 220, which iselectrically connected to a common ground, creates an electric fieldwhich causes structural plate 220 to tilt, or otherwise deflect, to theleft until the end of structural plate 220 contacts left overlyingstructure 240. In addition, as illustrated in FIG. 2B, contact bystructural plate 220 causes the horizontal portion of left overlyingstructure 240 to bow until the center of the horizontal portion nearsleft vibrational actuator 250.

Contact between structural plate 220 and left overlying structure 240 iseliminated as structural plate 220 is returned from the left tiltposition to the horizontal static position illustrated in FIG. 2A.Return to the horizontal static position is achieved by removing VR fromleft actuator 230 and right vibrational actuator 252. Under normalcircumstances, restoring forces associated with the interaction ofstructural plate 220 and pivot 224 cause structural plate 220 to returnto the horizontal static position. However, in some instances, stictionrelated forces are sufficient to overcome the restoring forces andstructural plate 220 remains tilted to the left even after VR isremoved.

The present embodiment of the invention disrupts such stiction relatedforces through vibration of left overlying structure 240. Such vibrationis produced coincident with the removal of VR. More specifically, whenVR is removed, the horizontal portion of left overlying structure 240elastically snaps from the bowed position (illustrated in FIG. 2B) tothe non-bowed position (illustrated in FIG. 2A). This movement, orlocalized vibration, of left overlying portion 240 disrupts any stictionforces, such that the restoring forces associated with structural plate220 and pivot 224 are sufficient to cause structural plate 220 to returnto the static horizontal position illustrated in FIG. 2A. In thisembodiment, the localized vibration is primarily along a verticalvector.

In some embodiments, left overlying structure 240 is engineered suchthat movement of the horizontal portion of left overlying structure 240from the bowed position illustrated in FIG. 2B to the non-bowed positionillustrated in FIG. 2A involves a damped oscillation between a boweddown position and a bowed up position. Thus, by removing VR, thehorizontal portion of overlying structure 240 oscillates between thepositions illustrated in FIGS. 2B and 2C until damping forces stop theoscillation and the left overlying structure comes to rest in thehorizontal position illustrated in FIG. 2A. Such oscillation, orlocalized vibration, sufficiently disrupts any stiction forces such thatthe restorative forces associated with structural plate 220 aresufficient to return structural plate 220 to the horizontal staticposition.

At this juncture, it should be recognized that a similar tilt to theright can be achieved and stiction forces resulting from such tilt canbe overcome using right actuator 232 and right stop 262.

In some embodiments, left actuator 230 and right vibrational actuator252 are electrically connected and are thus both actuated when VR isapplied. Similarly, right actuator 232 and left vibrational actuator 250can be electrically connected, such that both are actuated by theapplication of a voltage potential, VL. Thus, in some embodiments, thefunctionality of the actuators can be provided with minimal wiringand/or control logic. Alternatively, in some embodiments, left actuator230 and left vibrational actuator 250, as well as, left actuator 232 andleft vibrational actuator 252 are not electrically connected and can beactuated individually. This provides a degree of flexibility whenoperating structural plate micromirror system 200. In yet otherembodiments, left actuator 230 and left vibrational actuator 250 areelectrically connected and are thus both actuated when VL is applied.Similarly, right actuator 232 and right vibrational actuator 252 can beelectrically connected, such that both are actuated by the applicationof a voltage potential, VR.

In yet other embodiments, the functionality of left actuator 230 isprovided by left vibrational actuator 250, which allows left actuator230 to be eliminated. Similarly, in some embodiments, the functionalityright actuator 232 is provided by right vibrational actuator 252 andright actuator 232 is eliminated. Thus, for example, a left tilt ofstructural plate 220 is effectuated by applying VL to left vibrationalactuator 250 only, in the absence of left actuator 230. Such eliminationof left actuator 230 and/or right actuator 232 can provide similarfunctionality to systems including both actuators, while reducing thenumber of actuators, wiring, and/or the complexity of any control logic.

FIGS. 3A and 3B illustrate two embodiments where dimples and standoffstructures are used to promote the longevity of left stop 260, andsimilarly right stop 262. Referring to FIG. 3A, left overlying structure240 includes standoff structures 245 a, 245 b formed above dimple areas251 a, 251 b. Dimple areas 251 a, 251 b are formed by cutting outportions of left vibrational actuator 250. Formation of dimples 251 a,251 b can include removal of small portions of left vibrational actuator250 to provide clearance for standoff structures 245 a, 245 b. Onepurpose of standoff structures 245 a, 245 b is to prevent contactbetween overlying structure 240 and the underlying actuator, thusavoiding a short. For embodiments where standoff structures 245 a, 245 bare posts, dimple areas 251 a, 251 b can be circular or rectangular cutout areas of left vibrational actuator 250. Such cut out areas leaveleft vibrational actuator 250 contiguous, less only relatively smalldimple areas 251 a, 251 b.

Alternatively, standoff structures 245 a, 245 b can be bars formedacross the length of left overlying structure 240, in which case, dimpleareas 251 a, 251 b are formed across the length of left vibrationalactuator 250. Formation of such expansive dimples 251 a, 251 b,effectively sub-divides left vibrational actuator into sub-parts 250 a,250 b, 250 c.

Standoff structures 245 a, 245 b contact base layer 210 at dimple areas251 a, 251 b when the horizontal portion of left overlying structure 240is bowed toward left vibrational actuator 250 (similar to thatillustrated in FIG. 2A). By contacting base layer 210, standoffstructures 245 a, 245 b prevent left overlying layer 240 from contactingand potentially damaging left vibrational actuator 250. Further,standoff structures 245 a, 245 b prevent an electrical short betweenleft overlying structure 240 and left vibrational actuator 250. In thisway, the longevity of left stop 260 can be increased. Of course, it isrecognized that using such standoffs and dimples is similarly applicableto right stop 262.

FIG. 3B illustrates an alternative embodiment where standoffs 246 a, 246b are formed in dimple areas 251 a, 251 b on base layer 210. Similar tothe embodiment described in relation to FIG. 3A, standoff structures 246a, 246 b prevent left overlying structure 240 from physically contactingleft vibrational actuator 250. Also, electrical shorting between leftoverlying structure 240 and left vibrational actuator 250 is prevented.

FIG. 4 illustrates an embodiment of the present invention applied to astructural plate micromirror system 500. Specifically, FIG. 4illustrates structural plate micromirror system 500 with a structuralplate 520 in a static horizontal position. Structural plate 520 issupported above a base layer 510 by a pivot 524 and a micromirror 522 isdisposed on structural plate 520. Structural plate 520, includingmicromirror 522, can be deflected to either the right or the left abouta pivot point 526, which in some embodiments is located at the junctionof structural plate 520 and pivot 524.

A left vibrational stop 560 is located next to a left actuator 590 usedto deflect structural plate 522 to the left and a right vibrational stop562 is located next to a right actuator 591 used to deflect structuralplate 520 to the right. Structural plate 520 can be deflected to theleft such that it contacts left vibrational stop 560. Similarly,structural plate 520 can be deflected to the right such that it contactsa right vibrational stop 562.

In operation, left stop 560 is actuated by application of a (DC)voltage, VL. The potential difference between VL and structural plate520, which is electrically connected to a common ground, creates anelectric field which causes structural plate 520 to tilt, or otherwisedeflect, to the left until the end of structural plate 520 contacts leftstop 560. In addition, as will be more fully described in relation toFIGS. 5 through 6, the electric field created by applying VL to leftactuator 590 causes an elastic displacement of left stop 560.

Contact between structural plate 520 and left stop 560 is eliminated asstructural plate 520 is returned from the left tilt position to thehorizontal static position illustrated in FIG. 4. Return to thehorizontal static position is achieved by removing VL from left actuator590. Under normal circumstances, restoring forces associated withstructural plate 520 and pivot 524 cause structural plate 520 to returnto the horizontal static position. However, in some instances, stictionrelated forces are sufficient to overcome the restoring forces andstructural plate 520 remains tilted to the left even after VL isremoved.

The present embodiment of the invention disrupts such stiction relatedforces by vibrating left stop 560. Such vibration is produced coincidentwith the removal of VL. More specifically, when VL is removed, left stop560 elastically snaps from the displaced position to a static position.This movement, or localized vibration of left stop 560 disrupts anystiction forces, such that the restoring forces associated withstructural plate 520 are sufficient to cause structural plate 520 toreturn to the static horizontal position. In various embodiments, thelocalized vibration can be primarily along a vertical vector, primarilyalong a horizontal vector, or any other vector. Further, such vibrationcan be actively created by applying an alternating force, or passivelycreated by relying on the elasticity of the materials comprising thestructural plate and/or the stop.

Various embodiments which provide such localized vibration areillustrated in FIGS. 5 through 6. Referring to FIG. 5A, an embodiment ofleft stop 560 according to the present invention is illustrated. In thisembodiment, left stop 560 includes an actuator mass 561 supported abovebase layer 510 by a number of serpentine structures 564. In someembodiments, serpentine sturctures 564 are vertical serpentinestructures. In addition, left stop 560 comprises an actuator 590disposed above base layer 510 and next to stop mass 561.

In operation, VL is applied to actuator 590. Application of VL createsan electric field between left stop 560 and structural plate 520 (notshown) and between stop mass 561 and actuator 590. The electric fieldcauses structural plate 520 to deflect to the left until an end ofstructural plate 520 contacts stop mass 561. In addition, the electricfield causes stop mass 561 to displace toward actuator 590. Suchdisplacement can be both horizontal and vertical depending upon theplacement of actuator 590 relative to stop mass 561. Stop mass 561remains in this displaced position until VL is removed.

When VL is removed from actuator 590, the attraction between stop mass561 and actuator 590 is eliminated and actuator mass elastically snapsback to a static position. This involves a combination of horizontal andvertical movement, or localized vibration which disrupts any stictionrelated forces allowing the restorative forces associated withstructural plate 520 to return structural plate 520 to the statichorizontal position.

In some embodiments, the combination of stop mass 561 and serpentinestructures 564 are engineered such that removal of VL results in adamped oscillation of stop mass 561. During such oscillation, orlocalized vibration, stop mass 561 repeatedly moves away from actuator590 and subsequently back toward actuator 590 until the oscillation isentirely damped out and stop mass 561 comes to rest in a staticposition. This localized vibration occurring along various vectors,including a combination horizontal and vertical vector, providessufficient disruption of any stiction related forces to allow structuralplate 520 to return to the horizontal static position.

FIGS. 5B and 5C illustrate embodiments of the present invention wherethe localized vibration occurs primarily along a vertical vector.Referring to FIG. 5B, an embodiment of left stop 560 according to thepresent invention is illustrated. In this embodiment, left stop 560includes actuator 590 which is operable to cause structural plate 520(not shown) to deflect into contact with a deformable pad 1510.

In operation, VL is applied to actuator 590. Application of VL createsan electric field between actuator 590 and structural plate 520 (notshown). The electric field causes structural plate 520 to deflect to theleft until an end of structural plate 520 contacts deformable stop 1510as illustrated in FIG. 5C. Deformable stop 1510 bends to accommodatemovement of structural plate 520 toward base layer 510.

When VL is removed from actuator 590, the attraction between actuator590 and structural plate 520 is eliminated. Elimination of theattractive force allows deformable pad 1510 to elastically snap back tothe static position illustrated in FIG. 5B. This involves primarilyvertical movement, or localized vibration which disrupts any stictionrelated forces acting between deformable stop 1510 and structural plate520 and allowing the restorative forces associated with structural plate520 to return structural plate 520 to the static horizontal position.

In some embodiments, deformable stop 1510 is engineered such thatremoval of VL results in a damped oscillation of deformable stop 1510along a primarily vertical vector. During such oscillation, or localizedvibration, deformable stop 1510 repeatedly moves away from base layer510 and subsequently back toward base layer 510 until the oscillation isentirely damped out and deformable stop 1510 comes to rest in the staticposition. This localized vibration provides sufficient disruption of anystiction related forces to allow structural plate 520 to return to thehorizontal static position.

FIGS. 6A and 6B illustrate embodiments of the present invention wherethe localized vibration occurs primarily along a horizontal vector.Referring to FIG. 6A, an embodiment of left stop 560 according to thepresent invention is illustrated. In this embodiment, left stop 560includes an actuator mass 565 which is moveable across base layer 510and is tethered by a serpentine structure 566 to an anchor mass 567. Insome embodiments, actuator mass 565 is supported above base layer 510 bydimples (not shown). The dimples can be useful to reduce frictionbetween actuator mass 565 and base layer 510. Further, in someembodiments, serpentine structure 566 can be a comb drive actuator.

In operation, VL is applied to anchor mass 567. Application of VLcreates an electric field between left stop 560 and structural plate 520(not shown) and between actuator mass 565 and anchor mass 567. Theelectric field causes structural plate 520 to deflect to the left untilan end of structural plate 520 contacts actuator mass 565. In addition,the electric field causes actuator mass 565 to displace horizontallytoward actuator 590. Actuator mass 565 remains in this displacedposition until VL is removed.

When VL is removed from anchor mass 567, the attraction between actuatormass 565 and anchor mass 567 is eliminated and actuator mass 565elastically snaps back to a static position. This involves substantiallyhorizontal movement, or localized vibration which disrupts any stictionrelated forces allowing the restorative forces associated withstructural plate 520 to return structural plate 520 to the statichorizontal position. In some embodiments significant horizontal forcesbetween actuator mass 565 and structural plate 520 can cause structuralplate 520 to break. Thus, in some embodiments, the amount of horizontalmovement of actuator mass 565 is limited.

In some embodiments, a combination of actuator mass 565 and serpentinestructure 566 are engineered such that removal of VL results in a dampedoscillation of actuator mass 565 along a primarily horizontal vector.During such oscillation, or localized vibration, actuator mass 565repeatedly moves away from anchor mass 567 and subsequently back towardanchor mass 567 until the oscillation is entirely damped out andactuator mass 565 comes to rest in a static position. This localizedvibration provides sufficient disruption of any stiction related forcesto allow structural plate 520 to return to the horizontal staticposition.

FIG. 6B illustrates another embodiment of left stop 560 according to thepresent invention. In this embodiment, left stop 560 includes an stopmass 569 which is supported above base layer 510 by a number of supportdimples 591, 592 and tethered by a serpentine structure 580 to anactuator mass 570.

In operation, VL is applied to actuator mass 570. Application of VLcreates an electric field between left stop 560 and structural plate 520(not shown) and between stop mass 569 and actuator mass 570. Theelectric field causes structural plate 520 (not shown) to deflect to theleft until an end of structural plate 520 (not shown) contacts stop mass569. In addition, the electric field causes stop mass 569 to displaceprimarily along a horizontal axis toward actuator mass 570. Stop mass569 remains in this displaced position until VL is removed.

When VL is removed from stop mass 569, the attraction between stop mass569 and actuator mass 570 is eliminated and stop mass 569 elasticallysnaps back to a static position. This involves primarily horizontalmovement, or localized vibration which disrupts any stiction relatedforces allowing the restorative forces associated with structural plate520 to return structural plate 520 to the static horizontal position.

Similar to the embodiment discussed in relation to FIG. 6B, some of thepresent embodiments involve a damped oscillation which provides thelocalized vibration sufficient to overcome any stiction related forces.

4. Vibration Through Excitation by an Alternating Current (AC) Potential

The preceding embodiments each involve creation of localized vibrationthrough application and removal of a DC voltage potential. At thisjuncture, it should be noted that in any of the embodiments described inrelation to FIGS. 2 through 6, localized vibration can be created byapplication of an AC potential. For example, by using an AC voltage or apulsed DC voltage for VL in the embodiment described in relation to FIG.2, the frequency at which the horizontal portion of left overlyingstructure 240 bows and subsequently returns to the static position canbe selected by controlling the frequency of VL. It should be recognizedthat in various embodiments, the present invention can incorporateeither a DC voltage in the place of an AC voltage. Thus, for example,where VL is a voltage potential alternating between ground and ten (10)volts at a frequency of 60 Hz, left overlying structure 240 will bow andreturn to a static position at a rate of 60 Hz. Such voltages andfrequencies can be tailored to a particular application. Of course, theelasticity of the material forming left overlying structure 240 canaffect the rate and therefore should be selected accordingly. In suchembodiments, the localized vibration is provided at a frequencycorresponding to the frequency of the applied AC voltage.

Yet further embodiments of the present invention provide localizedvibration by exciting an actuator mass and/or a hard stop with an ACvoltage alternating at or near the natural frequency of the actuatormass and/or a hard stop. FIG. 7 illustrates an amplitude curve 700 forthe vibration of a mass excited by a driving force. The amplitude of avibration is noted on a vertical axis 705 and the frequency of thedriving force is noted on a horizontal axis 710. The peak of amplitudecurve 700 occurs at an amplitude value 715 where a frequency 720 of thedriving force is close to the natural frequency of the vibrating mass.Frequency 720 is often referred to as the resonant frequency. At theresonant frequency, the amplitude of the vibration is maximized,however, vibration is ongoing for frequencies on either side offrequency 720. By exciting the vibrating mass at or near the resonantfrequency, the amplitude of the vibration can be made very large throughrepeated application of a relatively small force.

Additionally, significant vibration can be achieved by exciting a massusing a driving frequency at or near one of the harmonic frequencies ofthe material comprising the actuator and/or hard stop. Thus, one ofordinary skill in the art will recognize that a number of differentdriving frequencies may be used to excite the mass.

Such an approach of creating localized vibration through application ofa driving force at or near the natural frequency of a material can beapplied to the embodiments described in relation to FIGS. 2 through 6.For example, an AC voltage, VL, can be applied to left stop 560 of FIG.4. Where the frequency of VL is at or near the natural frequency of thematerial comprising left stop 560, it will oscillate. Such oscillationsprovide the localized vibration sufficient to overcome stiction relatedforces. While the preceding example is described using an AC voltagepotential to excite the mass, it should be recognized by one skilled inthe art that other energy types may be used to excite the actuator. Forexample, a sound wave with a frequency at or near the natural frequencyof the material comprising the actuator may be used to excite theactuator to vibrate.

FIGS. 8A and 8B illustrate yet another embodiment of the presentinvention which is describe herein to provide localized vibration byapplication of an AC voltage with a frequency at or near the naturalfrequency of the vibrating mass. However, it will be recognized by anyone of skill in the art that the present embodiment can be used toprovide localized vibration by application of a DC voltage or by an ACvoltage not necessarily at or near the natural frequency of thematerial. Such localized vibration is provided consistent with methodsand operations of the previously described embodiments.

More specifically, FIG. 8A illustrates a structural plate micromirrorsystem 800 with a structural plate 820 in a static horizontal position.Structural plate 820 includes left serpentine structures 840 and rightserpentine structures 842, which are designed to promote vibration ofstructural plate 820. In some embodiments, structural plate 820 isvibrated according to the principles discussed in relation to FIG. 7.Similar to prior embodiments, structural plate 820 is supported above abase layer 810 by a pivot 824 and a micromirror 822 is disposed onstructural plate 820. Structural plate 820, including micromirror 822,can be deflected to either the right or the left about a pivot point826, which in some embodiments is located at the junction of structuralplate 820 and pivot 824.

A left actuator 860 is used to deflect structural plate 822 to the leftand a right actuator 862 is used to deflect structural plate 820 to theright. Structural plate 820 can be deflected to the left such that itcontacts base layer 810 or a hard stop disposed thereon. Similarly,structural plate 820 can be deflected to the right such that it contactsbase layer 810 or a hard stop disposed thereon. FIG. 8B provides a toplevel schematic diagram of structural plate 820, including left andright serpentine structures 840, 842 and micromirror 822.

In operation, left actuator 860 is actuated by application of a voltage,VL. In some embodiments, VL is initially a DC voltage potential whichcreates an electric field attracting structural plate 820 to tilt, orotherwise deflect to the left until an edge of structural plate 820contacts base layer 810 or a hard stop disposed thereon. Similar topreviously described embodiments, VL is then removed allowing structuralplate 820 to return to the static horizontal position illustrated inFIG. 8A. Again, however, stiction related forces occasionally preventsuch a return of structural plate 820 to the static horizontal position.

To overcome these stiction related forces, an AC voltage, VL′, isapplied to left actuator 860. The frequency of VL′ is chosen to be at ornear the natural frequency of left serpentine structures 840. Thealternating potential difference between VL′ and the common groundcoupled to structural plate 820 creates an alternating electric fieldand causes left serpentine structures to oscillate according theprinciples discussed in relation to FIG. 7. The alternating electricfield is insufficient to maintain structural plate 820 in contact withbase layer 810, but does create sufficient localized vibration todisrupt stiction related forces and allow the restorative forcesassociated with structural plate 820 to return structural plate 820 tothe horizontal static position.

As previously discussed, the embodiment described in relation to FIGS.8A through 8B can also be used to create localized vibration through theapplication of either a DC voltage or an AC voltage not necessarily nearthe natural frequency of any of the structures. For example, FIG. 8Cillustrates an embodiment where structural plate 820 is designed to flexat serpentine elements 840, 842. Thus, for example, when VL is appliedto left actuator 860 causing structural plate 820 to tilt to the left,structural plate 820 flexes at serpentine structures 840 as the end ofstructural plate 820 contacts base layer 810. The flex point associatedwith serpentine structures 840 stores energy which is released when VLis removed from left actuator 860. This release of energy causesstructural plate 820 to return to its straight static position. Inreturning to the static position, the end of structural plate 820 movesrelative to base layer 810. Such movement, or local vibration, issufficient to overcome stiction related forces, and the restorativeforces associated with structural plate 820 and pivot 824 act to returnstructural plate 820 to the static horizontal position.

In some embodiments, the release of energy from the flexure associatedwith serpentine elements 840 results in a damped oscillation asserpentine elements 840 repeatedly bow toward base layer 810 and awayfrom base layer 810 until the oscillation is finally damped out andstructural plate 820 comes to rest in a straight position. Suchoscillation results in a localized vibration at the point wherestructural plate 820 contacts base layer 810. This localized oscillationdisrupts stiction related forces and allows the restorative forces toreturn structural plate 820 to the static horizontal position.

Referring to FIGS. 8D and 8E, a system 2000 including a structural plate2012 disposed above pivot 2008 is disclosed. Structural plate 2012includes a right vibration mass 2043 attached via a right serpentinestructure 2042. Similarly, a left vibration mass 2041 is attached via aleft serpentine structure 2040. Structural plate 2012 can be deflectedto the right by energizing right actuator 2062 and similarly deflectedto the left by energizing left actuator 2060. When deflected to theright, structural plate 2012 contact a stop 2072. In addition, a rightvibration electrode 2063 and a left vibration electrode 2061 aredisposed under the respective right and left vibration masses 2043,2041.

In some embodiments, right vibration electrode 2063 is electricallyconnected to right actuator 2062. Similarly, left actuator 2060 iselectrically connected to left vibration electrode 2061. In otherembodiments, left actuator 2060 is electrically connected to rightvibration electrode 2063, while right actuator 2062 is electricallyconnected to left vibration electrode 2061. In yet other embodiments,all vibration electrodes 2061, 2063 are connected via a common bond pad(not shown).

As illustrated in FIG. 8D, structural plate 2012 is stuck due tostiction in a right tilt position with all actuators and vibrationelectrodes de-energized. To overcome the stiction between structuralplate 2012 and stop 2072, right vibration electrode is energized usingan AC voltage or a pulsed DC voltage. Application of this voltage causesright vibration mass 2043 to be attracted toward right vibrationelectrode 2063 and release. This is repeated as the applied voltagechanges state causing right vibration mass 2043 to vibrate. Suchvibration increases until the stiction between stop 2072 and structuralplate 2012 is overcome.

In embodiments where right vibration electrode 2063 is electricallyconnected to left actuator 2060, left actuator 2060 is energized inunison with the energization of right vibration electrode 2063.Energization of left actuator 2060 creates attraction between theactuator and structural plate 2012 which aids in overcoming thestiction. With the stiction overcome, restorative forces associated withstructural plate 2012 and pivot 2008 cause the structural plate toreturn to a static state as illustrated in FIG. 8E.

5. Vibration Through Mechanical Excitation

FIG. 9 illustrates an embodiment of a micromirror system 900 accordingto the present invention where an external element is used to createlocalized vibration at a point susceptible to stiction related forces.Micromirror system 900 includes a structural plate 920 deflected to aright tilt position. Structural plate 920 is supported above a baselayer 910 by a pivot 924 and includes a micromirror 922 disposed overit. A left actuator 960 and a right actuator 962 are included on eitherside of pivot 924. When activated, left and right actuators 960, 962cause structural plate 920 to tilt, or otherwise deflect in thedirection of the respective left or right actuator 960, 962.

In addition, micromirror system 900 includes a vibration beam 980supported above base layer 910 by a pivot 984. Vibration beam 980 can bebrought into contact with structural plate 920 through application of avoltage potential, VV, to a vibration actuator 990.

For purposes of discussion, it is assumed that a voltage, VR, wasinitially applied to right actuator 962 to cause structural plate 920 toassume the right tilt position illustrated in FIG. 9. VR was thenremoved, but structural plate 920 failed to return to a statichorizontal position due to stiction forces incident at the contactbetween structural plate 920 and base layer 910. To overcome suchstiction related forces, vibration beam 980 is brought into repeatedcontact with structural plate 920 through application of an AC voltage,VV. Such repeated contact results in a vibration local to the right sideof structural plate 920, which sufficiently disrupts stiction forces toallow restorative forces to return structural plate 920 to a horizontalstatic position.

6. Vibrating Multiple Actuators Simultaneously

Localized vibration according to the present invention can includevibrating a number of areas susceptible to stiction related forcessimultaneously. Thus, in some embodiments of the present invention, theright side of all structural plates in an array of structural plates maybe vibrated simultaneously according to the present invention. In suchan embodiment, all of the structural plates are not necessarily beingmoved from a right tilt position, however, all of the structural platesare nonetheless vibrated. Right actuators associated with each of thestructural plates which are to be switched from the right tilt positionare all de-energized. Thus, the only forces maintaining the structuralplates to be moved from the right tilt position are stiction relatedforces. Such stiction related forces are, however, sufficientlydisrupted by simultaneous localized vibration according to the variousembodiments of the present invention. Disrupting the stiction relatedforces allows the restorative forces associated with each of theindividual structural plates to return the respective structural platesto a horizontal static position.

In contrast, right actuators associated with structural plates which areto remain tilted to the right, continue to be activated while thelocalized vibration is performed. Such localized vibration temporarilyvibrates the various structural plates, but, the structural platesremain aligned and in the right tilt position due to the continuousactivation of the right actuators. Thus, structural plates which are toremain tilted to the right are largely unaffected by the localizedvibration.

Similarly, structural plates which were previously tilted to the leftare also unaffected by the localized vibration. As a structural platewhich is tilted to the left is not in contact with vibrating elementsassociated with the right of the structural plate, the localizedvibration can be performed without affecting the alignment of structuralplates tilted to the left. Thus, localized vibration may be applied to anumber of structural plates simultaneously, regardless of whether aparticular structural plate is to be switched or not. Such simultaneousapplication of localized vibration reduces the complexity of wiring andcontrol logic involved in overcoming stiction through localizedvibration.

FIG. 10 illustrates an embodiment of a structural plate system 1000where a number of left vibrating actuators 1020 and right vibratingactuators 1030 are connected as groups according to the presentinvention. More specifically, left vibrating actuators 1020 a, 1020 b,1020 c, and 1020 d are commonly wired to voltage potential VL.Similarly, right vibrating actuators 1030 a, 1030 b, 1030 c, and 1030 dare commonly wired to voltage potential VR. Each of the right and leftvibrating actuators 1020, 1030, are disposed beneath a correspondingstructural plate 1010. Each of structural plates 1010 are disposed abovea base layer (not shown) and supported by pivots 1040.

By applying potential VL, each of left vibrating actuators 1020 isvibrated. Similarly, each of right vibrating actuators 1030 are vibratedby application of potential VR. By interconnecting a number of vibratingactuators, stiction can be overcome through localized vibration throughthe use of minimal wiring and/or control logic. Further, such use oflocalized vibration can be accomplished without affecting structuralplates 1010 which are not to be moved from their existing tiltpositions.

7. Fiber-Optics Applications

a. Wavelength Router

Tilting micromirrors according to the embodiments described above, andtheir equivalents, may be used in numerous applications as parts ofoptical switches, display devices, or signal modulators, among others.One particular application of such tilting micromirrors is as opticalswitches in a wavelength router such as may be used in fiber-optictelecommunications systems. One such wavelength router is described indetail in the copending, commonly assigned U.S. patent application,filed Nov. 16, 1999 and assigned Ser. No. 09/442,061, entitled“Wavelength Router,” which is herein incorporated by reference in itsentirety, including the Appendix, for all purposes. The variousmicromirror embodiments may be used in that wavelength router or may beincorporated into other wavelength routers as optical switches where itis desirable to avoid stiction problems.

Wavelength routing functions may be performed optically with afree-space optical train disposed between the input ports and the outputports, and a routing mechanism. The free-space optical train can includeair-spaced elements or can be of generally monolithic construction. Theoptical train includes a dispersive element such as a diffractiongrating, and is configured so that the light from the input portencounters the dispersive element twice before reaching any of theoutput ports. The routing mechanism includes one or more routingelements and cooperates with the other elements in the optical train toprovide optical paths that couple desired subsets of the spectral bandsto desired output ports. The routing elements are disposed to interceptthe different spectral bands after they have been spatially separated bytheir first encounter with the dispersive element.

FIGS. 11A, 11B, and 11C are schematic top, side, and end views,respectively, of one embodiment of a wavelength router 10. Its generalfunctionality is to accept light having a plurality N of spectral bandsat an input port 12, and to direct subsets of the spectral bands todesired ones of a plurality M of output ports, designated 15(1) . . .15(M). The output ports are shown in the end view of FIG. 11C asdisposed along a line 17 that extends generally perpendicular to the topview of FIG. 11A. Light entering the wavelength router 10 from inputport 12 forms a diverging beam 18, which includes the different spectralbands. Beam 18 encounters a lens 20 that collimates the light anddirects it to a reflective diffraction grating 25. The grating 25disperses the light so that collimated beams at different wavelengthsare directed at different angles back towards the lens 20.

Two such beams are shown explicitly and denoted 26 and 26′, the latterdrawn in dashed lines. Since these collimated beams encounter the lens20 at different angles, they are focused towards different points alonga line 27 in a transverse plane extending in the plane of the top viewof FIG. 1A. The focused beams encounter respective ones of a pluralityof retroreflectors that may be configured according as contactlessmicromirror optical switches as described above, designated 30(1) . . .30(N), located near the transverse plane. The beams are directed back,as diverging beams, to the lens 20 where they are collimated, anddirected again to the grating 25. On the second encounter with thegrating 25, the angular separation between the different beams isremoved and they are directed back to the lens 20, which focuses them.The retroreflectors 30 may be configured to send their intercepted beamsalong a reverse path displaced along respective lines 35(1) . . . 35(N)that extend generally parallel to line 17 in the plane of the side viewof FIG. 11B and the end view of FIG. 2C, thereby directing each beam toone or another of output ports 15.

Another embodiment of a wavelength router, designated 10′, isillustrated with schematic top and side views in FIGS. 13A and 13B,respectively. This embodiment may be considered an unfolded version ofthe embodiment of FIGS. 11A-11C. Light entering the wavelength router10′ from input port 12 forms diverging beam 18, which includes thedifferent spectral bands. Beam 18 encounters a first lens 20 a, whichcollimates the light and directs it to a transmissive grating 25′. Thegrating 25′ disperses the light so that collimated beams at differentwavelengths encounter a second lens 20 b, which focuses the beams. Thefocused beams are reflected by respective ones of plurality ofretroreflectors 30, which may also be configured as contactlessmicromirror optical switches, as diverging beams, back to lens 20 b,which collimates them and directs them to grating 25′. On the secondencounter, the grating 25′ removes the angular separation between thedifferent beams, which are then focused in the plane of output ports 15by lens 20 a.

A third embodiment of a wavelength router, designated 10″, isillustrated with the schematic top view shown in FIG. 9. This embodimentis a further folded version of the embodiment of FIGS. 11A-11C, shown asa solid glass embodiment that uses a concave reflector 40 in place oflens 20 of FIGS. 11A-11C or lenses 20 a and 20 b of FIGS. 12A-12B. Lightentering the wavelength router 10″ from input port 12 forms divergingbeam 18, which includes the different spectral bands. Beam 18 encountersconcave reflector 40, which collimates the light and directs it toreflective diffraction grating 25, where it is dispersed so thatcollimated beams at different wavelengths are directed at differentangles back towards concave reflector 40. Two such beams are shownexplicitly, one in solid lines and one in dashed lines. The beams thenencounter retroreflectors 30 and proceed on a return path, encounteringconcave reflector 40, reflective grating 25′, and concave reflector 40,the final encounter with which focuses the beams to the desired outputports. Again, the retroreflectors 30 may be configured as contactlessmicromirror optical switches.

b. Optical-Switch Retroreflector Implementations

FIG. 14A shows schematically the operation of a retroreflector,designated 30 a, that uses contactless-micromirror optical switches.FIG. 14B is a top view. A pair of micromirror arrays 62 and 63 ismounted to the sloped faces of a V-block 64. A single micromirror 65 inmicromirror array 62 and a row of micromirrors 66(1 . . . A) inmicromirror array 63 define a single retroreflector. Micromirror arraysmay conveniently be referred to as the input and output micromirrorarrays, with the understanding that light paths are reversible. The leftportion of FIG. 14A shows micromirror 65 in a first orientation so as todirect the incoming beam to micromirror 66(1), which is oriented 90°with respect to micromirror 65's first orientation to direct the beamback in a direction opposite to the incident direction. The right halfof FIG. 14A shows micromirror 65 in a second orientation so as to directthe incident beam to micromirror 66(M). Thus, micromirror 65 is moved toselect the output position of the beam, while micromirrors 66(1 . . . M)are fixed during normal operation. Micromirror 65 and the row ofmicromirrors 66(1 . . . M) can be replicated and displaced in adirection perpendicular to the plane of the figure. While micromirrorarray 62 need only be one-dimensional, it may be convenient to provideadditional micromirrors to provide additional flexibility.

In one embodiment, the micromirror arrays are planar and the V-groovehas a dihedral angle of approximately 90° so that the two micromirrorarrays face each other at 90°. This angle may be varied for a variety ofpurposes by a considerable amount, but an angle of 90° facilitatesrouting the incident beam with relatively small angular displacements ofthe micromirrors. In certain embodiments, the input micromirror arrayhas at least as many rows of micromirrors as there are input ports (ifthere are more than one), and as many columns of mirrors as there arewavelengths that are to be selectably directed toward the outputmicromirror array. Similarly, in some embodiments, the outputmicromirror array has at least as many rows of micromirrors as there areoutput ports, and as many columns of mirrors as there are wavelengthsthat are to be selectably directed to the output ports.

In a system with a magnification factor of one-to-one, the rows ofmicromirrors in the input array are parallel to each other and thecomponent of the spacing from each other along an axis transverse to theincident beam corresponds to the spacing of the input ports. Similarly,the rows of micromirrors in the output array are parallel to each otherand spaced from each other (transversely) by a spacing corresponding tothat between the output ports. In a system with a differentmagnification, the spacing between the rows of mirrors would be adjustedaccordingly.

8. Conclusion

The invention has now been described in detail for purposes of clarityand understanding. However, it will be appreciated that certain changesand modifications may be practiced within the scope of the appendedclaims. For example, additional vibrational structures can be added toprovide additional aspects according to the present invention.Additionally, it should be recognized that a variety of functions can beperformed using the present invention. For example, a particularstructural plate may be switched from a right tilt position to a lefttilt position without first coming to rest in a horizontal staticposition. This can be accomplished through a combination of activationand de-activation of respective left and right actuators. Such acombination of activation will be readily apparent to one of ordinaryskill in the art from the preceding detailed description.

Thus, although the invention is described with reference to specificembodiments and figures thereof, the embodiments and figures are merelyillustrative, and not limiting of the invention. Rather, the scope ofthe invention is to be determined solely by the appended claims.

1. An electromechanical system, the system comprising: a structuralplate in contact with a stop; and an actuator activated by a force forcreating a movement of the stop relative to the structural plate,wherein the movement is sufficient to overcome stiction forces betweenthe structural plate and the stop.
 2. The system of claim 1, whereinactivating the actuator with a force causes the stop to displace from astatic position to a displaced position, and wherein the movementresults from elastic forces associated with the stop which cause thestop to displace from the displaced position to the static position whenthe actuator is de-activated.
 3. The system of claim 2, wherein themovement comprises an oscillation of the stop.
 4. The system of claim 3,wherein the oscillation comprises displacement of the stop from thedisplaced position passed the static position to an overshoot positionand back to the static position.
 5. The system of claim 1, wherein theforce comprises an alternating force having a frequency.
 6. The systemof claim 1, wherein the alternating force is an AC voltage or a pulsedDC voltage.
 7. The system of claim 5, wherein the oscillation comprisesa frequency at or about the frequency of the alternating force.
 8. Thesystem of claim 1, the system further comprising a base layer, whereinthe structural plate is supported above the base layer by a pivot andthe stop is disposed over the base layer.
 9. The system of claim 8, thesystem further comprising a micro-mirror disposed on the structuralplate.
 10. The system of claim 8, wherein the actuator is a firstactuator, the system further comprising a second actuator, whereinapplication of a DC voltage to the second actuator cause the structuralplate to displace and contact the stop.
 11. The system of claim 1,wherein the movement is primarily vertical relative to the base layer.12. The system of claim 1, wherein the movement is primarily horizontalrelative to the base layer.
 13. The system of claim 1, wherein themovement comprises a combination of horizontal and vertical movementrelative to the base layer.
 14. The system of claim 1, wherein theelectromechanical system is comprised by an optical routing apparatuscomprising a moveable micro-mirror.